Certain hospital beds include an occupant position monitoring system, also known as a patient position monitoring system or PPM system. An example PPM system is described in U.S. Pat. No. 6,208,250, the contents of which are incorporated herein by reference. The system disclosed in U.S. Pat. No. 6,208,250 has three levels of sensitivity which can be selected by a user, usually a caregiver. When the PPM system is armed, it activates an alarm if the position of the patient violates position criteria associated with the selected sensitivity level. The lowest sensitivity setting results in activation of the alarm only if the occupant actually exits the bed. A moderate sensitivity setting results in activation of the alarm if the occupant assumes a position on the bed consistent with an intent to exit. The most sensitive sensitivity setting results in activation of the alarm if the occupant merely moves away from a defined position on the bed, for example if the occupant migrates laterally away from the center of the bed and toward the left or right edge of the bed by more than an acceptable amount, or if the occupant sits up from a lying position. If the occupant is under no restrictions as to his or her movement, including being cleared to exit the bed without assistance or supervision, the caregiver may disarm the system, in which case the alarm remains inactive irrespective of occupant position.
The described system is useful for monitoring and regulating movement of patients whose movement and/or position on the bed needs to be restricted. However the functionality of the system cannot reasonably be extended. For example if the system were modified to command devices or functions other than the alarm (referred to herein as nonalarm devices or functions) in response to the movement and/or position of an occupant who is under no restrictions as to his or her movement and/or position, the modified system would also unnecessarily activate the alarm.
Accordingly, a solution is sought to the problem of extending the use of a PPM system to command nonalarm devices and/or functions without activating the alarm.